We use the conventions of Ref. [1]}. The gauge fields
in the broken phase are
\(W_\mu ^\pm = \frac{1}{2} \big ( W_\mu ^1 \mp i W_\mu ^2\big )\,, \qquad \begin{pmatrix}Z_\mu \\A_\mu \end{pmatrix} =\begin{pmatrix}c_w&s_w\\-s_w&c_w\end{pmatrix}\begin{pmatrix}W_\mu ^3\\B_\mu \end{pmatrix},\) 
